Some of this will depend on what you plan for future needs. Do you have the manual? That would be a place to start to get to know what is recommended but how much personally involved you want to get will vary.
From there, a six year old with those miles is not at all bad so what happens next is always a good question!
If one wanted to go big and really have somebody look it over, things like brakes come to mind and taking it somewhere for a good look at that is one point.
But for personal choice things to do, lubing almost everything that moves like door hinges and latches, getting to know what things do when starting and how they operate can be big. Small things like what does the furnace do when starting, so that you will know if it suddenly changes.
Lots of small points and many will likely just shake out as you learn the RV but those are ones I would want to know upfront. What does this switch do is better worked out BEFORE we need the switch!
2015 Winnebago Vista 31KE on 2014 chassis